This invention relates to apparatus for removing oversize from the hot material discharged from a rotary kiln used to produce sponge iron by a direct reduction of iron oxide containing materials, which apparatus comprises a stationary kiln head, which surrounds and is gas-tightly sealed to the discharge end of the rotary kiln, an oversize discharge device provided on the kiln head, and a discharge device for the particles which have passed through a sieve-like separator.
The material discharged from a rotary kiln consists of a mixture of sponge iron, surplus coal, ash and, possibly, desulfurizing agent. That material is discharged at a temperature of about 800.degree. to 1200.degree. C. In addition to particles of normal size, the discharged material may contain also oversize lumps, such as detached crusts, agglomerated portions of the charge or pieces of the refractory lining. Such oversize must be removed from the discharged material before the latter is melted. If the discharged material is to be charged in a hot state into the melting furnace, the oversize must be removed from the discharged material while it is in a hot state and an access of air to the discharged material must be prevented in order to avoid a reoxidation. In some cases the fines are also to be removed in a hot state by sieving before the material is charged into the melting furnace, and a reoxidation must be prevented in that case too.
Published German application Ser. No. 31 33 589 discloses a separator in which a coarse grate for removing the oversize is disposed in the kiln head and the oversize falls through a flap valve out of the kiln head. A vibrating sieve is disposed under the coarse grate. The fines fall through a chute into a cooling drum, and the desired product falls from the sieve through a chute into a transport container which is discharged into an electric furnace. In that arrangement the transport container may be overfilled and such overfilling will give rise to considerable problems. Besides, the rotary kiln must be stopped when the transportation of the product is disturbed.